Updating worksheet and move data to another worksheet

Hi guys,

I have a problem with my newest project. I will try to explain:

A)
I have an existing worksheet named "Existing data" with (let us say) 2 columns ("RecordID" and "SomeDate") and 10 rows. I would like this sheet to be updated with data from my sheet "New data" with the same number of columns as the previous. This new sheet will always have more rows than the previous. I would like to compare these two sheets. Compared by "RecordID" and if the "SomeDate" is newer than in the existing data OR if it is a new "RecordID", I need a vba code to:

1) Copy the headline + the "New data" row to a new sheet called: "Updated data".
2) Replace the "Existing data" row with the "New data" row.

B)
The headline + row replaced in 2) should be copied to a sheet called "Traceability".

For some reason,maybe lack of experience or Tuesdays(!), I can't figure this out...

Does anyone have some guidance, links, codes or constructive advise? It will be much appreciated!